The present invention relates generally to a tailgate assembly, and more specifically to a tailgate assembly having an tracking support member for the tailgate.
Work machines are used in earth moving operations to move material, such as dirt and rock, from one point to another. Two types of work machines are commonly used in the industry to perform this task: dump trucks and ejector trucks. Both types of trucks have a receptacle body to carry the material being moved. A dump truck tilts the body to release the material, and an ejector truck pushes the material out the back of the body with an ejector blade. Both dump trucks and ejector trucks may be provided with a tailgate. The tailgate serves to keep the material in the body until the operator wishes to release the material. Dump truck tailgates can be simple in design and operated by gravity and/or the weight of the material being dumped. Ejector truck tailgates are of particular interest, as this type of tailgate is normally powered, often with a hydraulic cylinder, and also may be used to help control the spreading of the material being ejected from the body.
International application No. WO 99/15357, published Apr. 1, 1999 (hereafter referenced as ""15357) discloses a tailgate assembly having an operating structure. The operating structure includes a pair of projecting brackets extending from and affixed to the exterior surface of the tailgate for supporting one end of a rigid link at a rotatable first pivot. The opposite end of the link may be pivotally attached at a second pivot to a coupling member which is shown as triangular in shape. A first comer of the coupling member is connected to the link at the second pivot. A second comer of the coupling member may be affixed to the underside of the truck body at a third pivot about which the coupling member rotates. A third comer of the coupling member includes a fourth pivot connected to one end of an extendable cylinder. The opposite end of the extendable cylinder is affixed at a fifth pivot to the underside of the truck body at a sixth pivot. As the cylinder extends and retracts, it moves the fourth pivot forward and rearward, respectively, thus moving the third comer of the coupling member and pivoting the member about its own third pivot at the second comer. The coupling member, in essence, acts as a bell crank in manipulating the tailgate.
While the ""15357 design has performed well, room for improvement exists. For example, the ""15357 design includes a number of pivot points, all of which need to be greased or maintained regularly and the jamming or binding of any of which would cause difficulty in operating the tailgate as intended. The triangular coupling member is under stress forces from many directions and must be made in a very robust manner to withstand the constant tension and/or compression forces. The triangular coupling member must be of a certain profile and arrangement to accommodate the linkage lengthsxe2x80x94this is shown in the drawings of ""15357 as being almost an equilateral triangle. Therefore, a large clearance space must be maintained to allow the coupling member to move. Also, should the ""15357 tailgate become bent or damaged, the relative movement of the pivot points may cause the operating structure to become inoperable to move the tailgate.
The present invention is directed to overcoming one or more of the problems set forth above.
In one aspect of the present invention, a tailgate assembly including a tailgate and an operating structure is provided. The tailgate is pivotally attached to a platform. The operating structure includes a linear actuator and a linking member. The linear actuator is attached to the platform. The linking member has a first end portion pivotally attached to the linear actuator, a fulcrum pivotally attached to the platform, and a second end portion attached to a tracking member. The tracking member is adapted to contact the tailgate and move vertically with respect to the tailgate.
In an aspect of the present invention, a work machine having a retention body and a tailgate assembly is disclosed. The tailgate assembly includes a tailgate pivotally attached to an end of the retention body and an operating structure. The operating structure includes a linear actuator attached to an underside of the retention body, a tracking member, and a linking member. The linking member has a first end portion pivotally attached to the linear actuator, a fulcrum pivotally attached to the retention body, and a second end portion attached to the tracking member.
In an aspect of the present invention, a method of operating a tailgate assembly of a work machine is disclosed. The tailgate assembly includes a tailgate and an operating structure. The tailgate has a lower portion and an upper portion vertically spaced from the lower portion. The operating structure has a linking member, an extendible linear actuator connecting a stationary surface and a first end of the linking member, and a tracking member connected to a second end of the linking member and slidably contacting a tailgate. The linking member is pivotally attached to the stationary surface at a fulcrum located between the first end and the second end. The method includes the steps of extending the linear actuator, rotating the linking member about the fulcrum in a first direction, and moving the tracking member from the lower portion of the tailgate to the upper portion.